Two-stroke cycle internal combustion engine



Sept. 8, 1931. P. scHMALJoHANN TWO-STROKE CYCLE I NTERNAL COMBUSTION ENGINE Filed Jan. 3. 1950 r Jaw-neg.-

PAUL SCI-IMALJOHANN, OF KIEL, GERMANY, ASSIGNOR TO Patented Sept. 8, 1931 UNITED STATES PATENT oFFiCB CEN TRA HANDELS- & IN-

DUSTRIE A.G., OF CHUR, SWITZERLAND, A CORPORATION 0F SWITZERLAND TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE Application filed January 3, 1930, serial No.

My invention relates to improvements in tW-str0ke cycle internal combustion engines, and more particularly in engines of the type comprising a plurality of cylinders disposed 5 radially of one another and having a common central combustion chamber. In `engines of this type the pistons or plungers are formed yat their inner ends 4with gable roof-shaped bottoms, for reducing as far as possible the size of the combustion chamber, which is particularly important in engines of the Diesel type the combustion chamber of which must be as small as possible.

In two-stroke cycle engines of this type in which the scavenging ports are disposed all around the circumference of the cylinder the said gable roof-shaped form ofthe pistons interferes with scavenging, the said gable roof-shaped bottoms deflecting the scavenging air injected into the cylinders through the said ports towards the axial portions of the cylinders, so that in the outer portions whirls are produced and the scavenging is unsatisfactory.

The object of the improvements is to provide an engine in which this objectionV is obviated, and with this object in view my invention consists in disposing the intake ports for scavenging air exclusively along the inclined margins of the bottoms of the pistons and so that the scavenging air is injected into the cylinders in a direction substantially parallel to the ridges or meeting portions of the gable roof-shaped faces of the bottoms of the pistons. When thus disposing the intake ports the currents of scavenging air injected into the cylinders impinge upon each other without being` deflected by the gable roofshaped bottoms of the pistons, and the kinetic energy of the said currents is largely annihilated, so that the cylinders are completely lilled with scavenging air, and the said air acts in the manner of pistons filling out the whole cross-sectional areas of the cylinders and scavenging the combustion gases from the same.

In the preferred construction the scavenging ports are disposed longitudinally of the cylinders so that they are completely uncovered by the pistons, and so that when 4178,31?, and in Germany January 5, 1929.

For the purpose of explaining the inven- Y tion an example embodying the same has been shown in the accompanying drawings in which the same reference characters have been used in all the views to indicate corresponding parts. In said drawings,

Fig. l is a sectional elevation of the engine,

Fig. 2 is a detail longitudinal sectionalv elevation on an enlarged scale showing a part of one'ofthe cylinders,

Fig. 3 is a longitudinal sectional elevation taken on the line 3 3 of Fig. 2, and

Fig. 4 is a cross-sectional View taken on the line 1- 4 of Fig. 3 and looking in the direction of the long arrow.

In the exampleshown in the figures the two-stroke cycle internal combustion engine may be assumed to operate on the Diesel principle, and it comprises three cylinders a disposed radially of eachother and connected or'made integral with one another at their inner ends to provide a combustion cha-mber' c. Within the cylinders pistons b are mounted the bottoms of which are gable roofshaped, the said bottoms comprising outer portions al inclined relatively to each other and to the axes of the cylinders and rounded or ridge portions c connecting the said inclined portions. While the term gable roofshaped is used herein to define the shape of the outer end of the pistons, it will be understood that this expression isused only for convenience and brevity. The actual preferred shape comprises two A substantially plane surfaces inclined to one another and joined by a curved portion, or ridge, as best shown in Figs. 2 and 4, or even a cylindrical-convex or vaulted shape as shown in Figs. 1 andy 3, and for want of a better term the expression gable roof-shaped in this specification and claims is to be undermivv stood as including all such shapes. Thus, when the pistons' are at their inner dead centre positions the said gable roof-shaped bottoms reduce the volume of the combustion chamber.

The scavenging ports f of the cylinders a are disposed parallel to the portions e of the bottoms of the pistons and to the faces (l, and they extend over a part only of the circumference of the cylinders, as is best showny in Fig. 4. Thus, there are two groups of scavenging ports j which are opposed to each other,`and which are located at the parts of the cylinders adjacent to the inclined margins of the faces l and e. Further, the slots f are disposed so that the controlling edges follow the form of the gable roof-shaped bottoms (Z, e of the pistons, as is shown in Fig. 3. Therefore, all the ports f are simultaneously uncovered by the pistons b.

With reference to the outer dead Centre positions of the pistons o the scavenging ports 7 are disposed in the cylinder a so that in the outer dead centre positions of the pistons the controlling edges of the piston bottoms CZ, e are at a distance from the outer edges of the ports In the example shown in the figures in two of the cylinders a the ports 7 act as scavenging ports, while in the third cylinder the ports g act as exhaust ports.

lNhen the scavenging ports f of the cylinders ay are uncovered by the pistons b moving outwardly air is injected through the said ports into the cylinders, the currents of air being parallel to the ridges c and the faces (Z of the bottoms of the piston. Therefore the said currents of air are not deflected by the gable roof-shaped bottoms, and the currents of air injected through the opposing groups of ports f impinge upon each other so that their kinetic energy is largely annihilated, and the portion of the cylinder a located internally of tlie bottoms d, e is completely filled with scavenging air. By the ,following scavenging air the said air is driven into the cylinders a filling out the whole cross-sectional areas thereof and acting as air pistons driving out the combustion gases through the slots g.

- After the scavenging ports f have been completely uncovered by the pistons b the said pistons continue their outward stroke through a. distance m shown in 3, and upon the following inward stroke of the pistons (l, e the controlling edges of the bottoms of the said pistons begin to cover the outer edges of the scavenging ports only after they have performed the portion m of their stroke. Thus during the major part of the scavenging period the controlling edges of the pistons b are away from the scavenging ports f, so that during the ysaid portion of the pe- Yriod the currents of air injected through the ports f are not deflected by the edges of the pistons.

The improvements may be used in twostroke cycle internal lcombustion engines comprising three or more pistons and having a common combustion chamber.

I claim:

l. A two-stroke cycle internal combustion engine, comprising more than two cylinders disposed radially of one another and having a common central combustion chamber, pistons reciprocating in said cylinders and having gable roof-shaped inner bottoms, andl two similar and oppositely located groups of scavenging ports disposed parallel to the ridges or meeting portions of the gable roof-shaped portions of the inner faces of the bottoms of the pistons, said groups being located at the opposite gable sides.

l2. A two-stroke cycle internal combustion engine, comprising more than two cylinders disposed radially of one another and having a common central combustion chamber, pistons reciprocating in said cylinders and having gable roof-shaped inner bottoms, andtwo similar and oppositely located groups of scavenging ports disposed parallel to the ridges or meeting portions of the gable roofshaped portions of the inner faces of the bottoms of the pistons and at the opposite gable sides of the pistons and so disposed that all the ports are uncovered simultaneously by the pistons.

3. A two-stroke cycle internal combustion engine, comprising more than twol cylinders disposed radially of one another and having a common central combustion chamber, pistons reciprocating in said cylinders and having gable roof-shaped inner bottoms, and two separate'groups of scavenging parts located at the gable sides and disposed parallel to the ridges or meeting portions of the gable roofshaped portions of the inner 'faces of the bottoms of the piston, said ports being so disposed relatively to the pistons and axially of the cylinders that inthe outer dead centre positions of said pistons the leading edges thereof are spaced from the outer edges of said ports.

In testimony whereof, I affix my signature.

PAUL SCHMALJOHANN. 

